1. Field of the Invention
The present invention relates to a refrigeration system for air-conditioners including a refrigeration cycle which employs a decompressing tube as decompressing means such as an orifice-tube or a capillary tube, and also relates to a condenser for use in a decompressing-tube system.
2. Description of Related Art
Generally, as a refrigeration system to be adopted for car air-conditioners or the like, the following refrigeration systems are well known: (1) an expansion-valve type refrigeration system including an automatic thermal expansion valve (TXV) as a decompressing means (hereinafter referred to as xe2x80x9cexpansion valve systemxe2x80x9d); and (2) an orifice-tube type refrigeration system (CCOT) including a decompressing tube as decompressing means such as an orifice-tube or a capillary tube (hereinafter referred to as xe2x80x9corifice-tube systemxe2x80x9d or xe2x80x9cdecompressing-tube systemxe2x80x9d).
As shown in FIG. 13, in the orifice-tube system, the gaseous refrigerant of high temperature and high pressure from the compressor 1 flows into the condenser 2 to be condensed therein. Then, the condensed refrigerant passes through the orifice-tube 3 to be decompressed and then flows into the evaporator 4. In the evaporator 4, the condensed refrigerant exchanges heat with the ambient air to be evaporated, and then is introduced into the accumulator 5. In the accumulator 5, only the gaseous refrigerant is separated from the refrigerant introduced in the accumulator 5, and the gaseous refrigerant returns to the aforementioned compressor 1. Thus, a refrigeration cycle is formed.
As compared with the expansion valve system, this orifice-tube system has fewer components and can be fabricated by fewer steps. Furthermore, the orifice-tube system is simple in structure and low in manufacturing cost.
The orifice-tube system is, however, inferior in response to load fluctuations.
That is, in the orifice-tube system, a liquefied refrigerant R stagnates at the subcooling area ranging from near the inlet of the orifice-tube 3 to the outlet of the condenser 2. This liquefied refrigerant R increases when the thermal load of the condenser 2 is small. For example, when an automobile mounting this refrigeration system is running at a high speed, the thermal load of the condenser 2 is small because of an enough amount of ventilation. In this case, the condenser performance can be fully demonstrated, resulting in an enhanced condensation of the refrigerant therein.
By the way, the amount of refrigerant passing through the orifice-tube 3 (i.e., circulation amount of refrigerant) is constant, and the amount of refrigerant passing through the orifice-tube 3 is limited. Accordingly, in cases where the thermal load of the condenser decreases suddenly, for example, when the running speed of the car is changed from a low-speed to a high-speed, the amount of liquefied refrigerant increases suddenly, and the subcooling area spreads even in the condenser 2. As a result, a large amount of liquefied refrigerant is temporarily accumulated in the condenser 2. When a large amount of liquefied refrigerant is accumulated in the condenser 2, the condensation of refrigerant will not be performed in the liquefied refrigerant stagnated portion. Accordingly, the effective area for condensing the refrigerant decreases, which in turn decreases the condenser performance.
To the contrary, in cases where the thermal load of the condenser increases suddenly, for example, when the running speed of the car is changed from a high-speed to a low-speed, the refrigerant is not condensed smoothly in the condenser 2. As a result, the amount of liquefied refrigerant accumulated in the outlet side portion in the condenser 2 decreases, resulting in insufficient subcooling degree of the liquefied refrigerant. This deteriorates the condenser performance temporarily. As will be apparent from the above, the orifice-tube system is inferior in response characteristic to load fluctuations, and cannot obtain sufficient refrigeration performance.
It is an object of the present invention to provide a refrigeration system that is excellent in response characteristic to load fluctuations and can obtain sufficient refrigeration performance irrespective of load fluctuations.
It is an object of the present invention to provide a condenser for use in a decompressing-tube system that is excellent in response characteristic to load fluctuations and can obtain sufficient refrigeration performance irrespective of load fluctuations.
Another object of the present invention will be apparent from the following embodiments.
According to the first aspect of the present invention, a refrigeration system having a refrigeration cycle, comprises:
a compressor for compressing a refrigerant;
a condenser for condensing the refrigerant compressed by the compressor;
a decompressing tube for decompressing the refrigerant condensed by the condenser;
an evaporator for evaporating the refrigerant decompressed by the decompressing tube; and
an accumulator for separating a gaseous refrigerant from the refrigerant evaporated by the evaporator,
wherein the condenser includes a refrigerant inlet for introducing the refrigerant compressed by the compressor, a refrigerant outlet for discharging the refrigerant condensed by the condenser, a refrigerant passage for leading the refrigerant introduced from the refrigerant inlet to the refrigerant outlet while condensing the refrigerant, and decompressing means provided at a part of the refrigerant passage to decompress the refrigerant passing through the decompressing means.
In this refrigeration system, when the thermal load of the condenser decreases, the condensation of refrigerant in the condenser is enhanced at the upstream side of the decompressing means, and therefore only the completely liquefied refrigerant passes through the decompressing means. Thus, the resistance of the refrigerant passing through the decompressing means decreases, thereby increasing the flow rate. Accordingly, at the upstream side of the decompressing means and the downstream side thereof, the condensation of refrigerant is performed efficiently. Thus, the performance of the condenser is sufficiently demonstrated.
To the contrary, when the thermal load of the condenser increases, the condensation of refrigerant in the condenser deteriorates at the upstream side of the decompressing means, and therefore incompletely liquefied refrigerant passes through the decompressing means. At this time, the amount of gas in the refrigerant increases, i.e., the volume of the refrigerant passing through the decompressing means increases, resulting in increased flow resistance of the refrigerant passing through the decompressing means, which in turn decreases the flow rate. As the flow rate decreases in this way, the condensation load at the upstream side of the decompressing means decreases. Accordingly, the condensation will be performed fully, resulting in enhanced condenser performance.
As will be apparent from the above, since the refrigerant flow rate can be appropriately adjusted in response to fluctuations of thermal load in the condenser, this refrigeration system is excellent in response characteristics to load fluctuations. Accordingly, sufficient refrigeration performance can be obtained.
In this refrigeration system, an orifice-tube can be suitably used as the decompressing tube.
Furthermore, in this refrigeration system, it is preferable that at least a part of the condensed refrigerant is evaporated by the decompressing means and then re-condensed.
That is, in this refrigeration system, it is preferable that at least a part of the refrigerant condensed at an upstream side of the decompressing means in the refrigerant passage is decompressed by the decompressing means into a low-pressure gaseous refrigerant, and the low-pressure gaseous refrigerant is re-condensed at a downstream side of the decompressing means in the refrigerant passage.
According to the second aspect of the present invention, a refrigeration system having a refrigeration cycle in which a refrigerant is compressed into a compressed refrigerant, the compressed refrigerant is condensed into a condensed refrigerant, the condensed refrigerant is decompressed by giving passage resistance into a decompressed refrigerant, the decompressed refrigerant is evaporated into an evaporated refrigerant, and then a gaseous refrigerant is separated from the evaporated refrigerant and re-compressed, wherein a decompressing passage for decompressing the refrigerant is provided at a part of a refrigerant passage in which the compressed refrigerant is condensed.
In this refrigeration system, in the same manner as in the aforementioned system, since the flow rate of the refrigerant is appropriately adjusted by the decompressing passage in response to fluctuations of thermal load, the response characteristics to load fluctuations is excellent, and sufficient refrigeration performance can be obtained.
According to the third aspect of the present invention, as the condenser in the refrigeration system according to the aforementioned first and second aspects of the present invention, the so-called multi-flow type heat exchanger is employed.
That is, a refrigeration system having a refrigeration cycle, comprises:
a compressor for compressing a refrigerant;
a condenser for condensing the refrigerant compressed by the compressor;
a decompressing tube for decompressing the refrigerant condensed by the condenser;
an evaporator for evaporating the refrigerant decompressed by the decompressing tube; and
an accumulator for separating a gaseous refrigerant from the refrigerant evaporated by the evaporator,
wherein the condenser includes:
a pair of headers disposed in parallel with each other at a certain distance;
a plurality of heat exchanging tubes disposed between the pair of headers with opposite ends thereof connected with the headers;
a partition provided in the header to group the plurality of heat exchanging tubes into a plurality of passes constituting a refrigerant passage through which the refrigerant passes in turn, the plurality of passes including a first pass and a final pass; and
decompressing means which is disposed at a part of the refrigerant passage between the first pass and the final pass to decompress the refrigerant passing through the decompressing means.
In this case, in the same manner as in the aforementioned system, the flow rate of refrigerant is appropriately adjusted by the decompressing means in response to fluctuations of thermal load. Thus, the response characteristic is excellent, and sufficient refrigeration performance can be obtained.
In this refrigeration system, an orifice-tube can be suitably used as the decompressing tube.
Furthermore, in this refrigeration system, it is preferable that the plurality of passes include the first pass, the final pass and one or a plurality of intermediate passes located between the first pass and the final pass, and wherein the one or a plurality of intermediate passes constitute a decompressing pass constituting the decompressing means.
In this case, a heat exchanging tube can be used as the decompressing means as it is. Thus, it is not necessary to attach additional components, and therefore the structure can be simplified.
In this refrigeration system, it is preferable that the intermediate pass located immediately before the final pass constitutes the decompressing means, that a total passage cross-sectional area of the decompressing pass is smaller than that of each pass located immediately before and after the decompressing pass, and that the number of heat exchanging tubes constituting the decompressing pass is smaller than that of each pass located immediately before and after the decompressing pass.
In these cases, the decompression effects can be effectively obtained by the decompressing means.
According to the fourth aspect of the present invention, a condenser for use in a decompressing-tube system constituting a refrigeration cycle which includes a compressor, a decompressing tube, an evaporator and an accumulator, comprises:
a refrigerant inlet for introducing a refrigerant;
a refrigerant outlet for discharging the refrigerant;
a refrigerant passage for leading the refrigerant introduced from the refrigerant inlet to the refrigerant outlet while condensing the refrigerant; and
decompressing means which is provided at a part of the refrigerant passage to decompress the refrigerant passing through the decompressing means.
In this condenser, in the same manner as in the aforementioned cases, the flow rate of refrigerant is appropriately adjusted by the decompressing means in response to fluctuations of thermal load. Thus, the response characteristic is excellent, and sufficient refrigeration performance can be obtained.
In this condenser, the so-called multi-flow type condenser can be used.
According to the fifth aspect of the present invention, a condenser for use in a decompressing-tube system constituting a refrigeration cycle which includes a compressor, a decompressing tube, an evaporator and an accumulator, comprises:
a pair of headers disposed in parallel with each other at a certain distance;
a plurality of heat exchanging tubes disposed between the pair of headers with opposite ends thereof connected with the headers;
a partition provided in the header to group the plurality of heat exchanging tubes into a plurality of passes constituting a refrigerant passage through which the refrigerant passes in turn, the plurality of passes including a first pass and a final pass; and
decompressing means which is disposed at a part of the refrigerant passage between the first pass and the final pass to decompress the refrigerant passing through the decompressing means.
In this condenser, in the same manner as in the aforementioned cases, the response characteristic is excellent, and sufficient refrigeration performance can be obtained.
In this condenser, it is preferable that the plurality of passes include the first pass, the final pass and one or a plurality of intermediate passes located between the first pass and the final pass, and wherein the one or a plurality of intermediate passes constitute a decompressing pass constituting the decompressing means.
In this case, a heat exchanging tube can be used as the decompressing means as it is.
Other objects and the features will be apparent from the following detailed description of the present invention with reference to the attached drawings.